// const fs = require('then-fs');

import fs from 'then-fs';

fs.readFile('./files/a.txt', 'utf-8')
  .then(res1 => {
    console.log(res1.length);
    return fs.readFile('./files/b.txt', 'utf-8');
  })
  .then(res2 => {
    console.log(res2.length);
    return fs.readFile('./files/c.txt', 'utf-8')
  })
  .then(res3 => {
    console.log(res3.length);
  })
  .catch(err => {
    console.log(err);
  })